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Hypothetical appearance of a secret postwar turbojet-powered STOL Skimmer. Although no documentation has surfaced to suggest such an aircraft existed, there have been various suggestions that propellers could have been replaced by jet engines. Bill Rose One final attempt to refine the Skimmer was made by a Norfolk, Virginia-based aero- nautical designer called John J Sullivan, who produced plans in 1954 for a new aircraft that evolved from the earlier work undertaken by Zimmerman. He incorporated a complex sys- tem of folding supports that allowed the air- craft to take off and land in a vertical position, with a cylindrical rotating cockpit that would move through 90° during transition to level flight. The size of this design was somewhat larger than the Skimmer, with various propul- sion options discussed that included pro- pellers and jet engines in pods. Drawings show a complex design that would have rep- resented a serious challenge to most engi- neers and Sullivan’s study never progressed beyond the paperwork stage. When Vought relocated to Texas in 1947, Zimmerman rejoined NACA at Langley, where he resumed his work on wind tunnel testing and began to experiment with simple compact VTOL platforms that could be flown with com- parative ease by an average person. A small demonstrator called Flying Shoes was com- pleted and this used a fan lift arrangement, with the pilot standing upright above the platform and controlling its movement by leaning his body in the desired direction of flight. Zimmer- man continued to improve the design and, dur- ing 1948, Stanley Hiller of Hiller Helicopters purchased the rights to the Flying Shoes. Zimmerman then started work on a small platform called the Jet Board, which was powered by compressed air. This was fol- lowed by a rotor-driven version called Whirligig, which flew on 21st October 1953. Hiller and De Lackner Helicopters pursued personal flying platforms based on Zimmer- man’s research, but serious technical prob- lems and safety issues prevented these ideas from progressing beyond prototypes. In 1952, Zimmerman became a member of the Brown Hypersonic Group that studied pro- posals for trans-atmospheric vehicles, which finally led to the North American X-15 rocket- plane. Six years later Zimmerman joined NACA’s Space Task Group, which produced the basic specification for the Mercury space capsule and planned the Apollo project. In 1962 he became NASA’s Director of Aeronau- tics, remaining in this post until 1967 when he retired. Zimmerman died on 5th May 1996. 35 Early Circular-Winged Aircraft